Single-phase motor.



E. F. W. ALEXANDERSON.

SINGLE PHASE MOTOR.

APPLICATION I-ILED DEC). 26, 1907.

920,710, Patented May 4, I909.

W'rtmssses: inventor:

66W? 571 )M. Ern stFWfilex under son,

ERNST r. w. ALExANDnRsonor PATENT. OFFICE.

SOHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.v

SINGLE-PHASE MOTOR.

Specification of Letters Patent. 7

Patented May 4, 1909.

Application filed December 26, 1907. Serial No: 408,143.

5 Schenectady and State of New York, ave

invented certain new and useful Improve ments in Single-Phase Motors, of which the following is a specification.

My invention relates to single-phase motors 0 of the commutator type, and its object is to improve the commutation, efficiency and power-factor of such motor There is one well-known type of motor,

- which is sometimes called the compensated repulsion motor, in which the stator is provided with an inducing winding, and thearmature with two sets of commutator brushes; one short-circuiting the armature on the line of magnetization of the inducing winding, and the other displaced ninety electrical degrees from the first set, and serving as means for supplying to the armature the exciting current of the motor. Such a motor, as compared with the ordinary repulsion motor, where the exciting or cross-field is produced by a winding on the stator, has a igher power-factor, because the electromotive force induced in the, armature winding between the exciting brushes, due to rotation in the field of the inducing winding,tends to neutralizethe self-induction oi the exciting circuit,that is, the circuit formed by the armature winding between the exciting brushes. is for this reason that the motor is frequently termed a compensated repulsion motor. The commutation of this type of motor is excellent at synchronism, if the I motor is properly designed, but in passing above synchronism the commutation rapidly becomes poor.

In-m prior application Serial No. 383,807, filed Ju y 15, 1907, I have disclosed a ty e of motor having inducing and exciting windings on the stator, inwhich the armature is shortcircuited at starting, while for high speeds a shunt voltage is impressed on the armature and exciting winding in series. The purpose of impressing theshunt voltage on the armature is to reduce the amount of the inducing field, which assists] commutation at low speeds, but becomes excessive in its efiect on commutation sithigh speeds. The purpose of including the exciting winding in circuit with the armature and the shunt voltage is to provide for the effect of commutation reactance. The reactance' of the exciting winding in the armature circuit roduces leakage fields which, when out by t e armature coils short-circuited by the brushes in commutetion, induce in those coils electromotive forces which neutralize the electromotive force of commutation reacts-nee. This motor, if properly designed, has excellent commutation at very high speeds, but its powerfactor is somewhat lower than that ol' the compensated repulsion motor.

My present invention consists in combin ing the advantages of both types of motors briefly described above. I accom lish this by providing the motor both wit citing winding on the stator and with exciting brushes. Since a part of the excitation is produced in the armature by the cur rent supplied through the exciting brushes,

the power-factor is higher than if all the excitation were produced by the exciting winding on the stator, while the presence oi the exciting winding on the stator makes it possible to im ress a shunt voltage on the main armature rushes and the exciting wind-ing in series, so as to obtain excellent commutation at high speeds.

My invention will best be understood by reference to the accompan ing drawing, which shows diagrammatica Y a motor-arranged in accordance with my invention.

In the drawing, A represents diagrammatically a motor armature, whichis rovided with main commutator brushes B and auxiliary or exciting brushes 6 b.

' 0 represents the inducing winding on-the stator, which produces a magnetization in line with the main brushes B B.

D represents the exciting winding on the stator producing a magnetization in line with the exciting brushes 1) b.

E represents a transformer for supplying current to the motor.

F representsa transformer having-its primary mseries with the main brushes B -B, andits secondary in series with the exciting brushes 7) b. The exciting'brushes are thus,

connected in series with the main brushes through the transformer F.

G represents a controlling switch for the motor, Which is shown diagrammatically with its contacts developed on a plane surface;

- motor, consequently starts like a repulsion and 383,807,

tor type motor, the current induced in the armature between the main brushes B B being supplied directly to the exciting winding D and through the transformer to the exciting brushes 1) b; When the motor has started,

and the switch G is moved to its second posia small shunt voltage, derived from the transformer E, is included inthe circuit of tion,

the main brushes and the exciting winding for the purpose of improving the commutai tion, as has been explained. For'operation at higher speeds tlieswitch G is moved to its third and fourthpositions, increasing the amount of the shunt voltage impressed on the armature and exciting winding, and thereby adapting the motor for good commutation at those higher speeds.

I have shown the motor diagrammatically. It will be understood that in practice the that of the usual direct-current motor, while the inducing winding C would be distributed, as iscustomary in alternating-current repulsion motors. Furthermore, in order that the full benefits' of my invention may be obtained with respect to commutation the armature winding should be given a pitch corresponding to the portion of the periphery of the stator over which the inducing windingC is distributed for reasons fully set forth in my prior ap lications, Serial Nos. 371,320 ed, respectively, May 1, 1907, and July 15, 1907.

What I claim as new and desire to secure by Letters Patent of the United States, is,

l. A single-phase motor of the commutator type having inducing and exciting windings on the stator connected in series with each other, main commutator brushes on the hne oi magnetizat on of the induclng WlIlCllDg connected in series with both stator wind ings, exciting brushes on the line of magnetization of the exciting winding, and means for impressing a shunt voltage on the exciting winding and main brushes in series.

2. A single-phase motor of the commute.

having inducing and exciting windings on the, stator connected in series with each other, main commutator brushes on the line of magnetization of the inducing winding connected in series with both stator windings,

motor armature would be constructed like exciting brushes on the line of magnetization of the exciting winding, and means for im- 3.- A single-phase motor of the comm utator type having inducing and exciting windings on the stator connected in series with each other, main commutator brushes en the line of magnetization of the inducing winding connected in series with both stator windings, exciting brushes on the line of magnett zation of the exciting winding, connections for placing the mainbrushes and exciting winding in a local closed circuit at starting, and means for introducing a shunt voltage into said closed circuit when the motor has started.

4. A single-phase motor of the commutator type having inducing and exciting windings on the stator connected in series with each other, main commutator brushes on the line of magnetization of the inducing winding connected in series with both stator windings, exciting brushes on the line of magnetization of the exciting winding, and a transi'ornier having its primary in series with the main brushes and its secondary in series with the exciting brushes. 5. A singlephase' motor of the commutatar type having inducing and exciting wind ings on the stator connected in series with each other, main commutator brushes on the line of magnetization oi the inducing winding connected in series with both stator windings, exciting brushes on the line oi magnetization of the exciting winding, a transformer having its primary in series with the main brushes and its secondary in series with the exciting brushes, and means for impressing a shunt voltage on the main brushes, exciting winding, and transformer primary,in series.

6. A single-phase motor of the coinmuta tor type having inducing and exciting windings on the stator connectedin series with each other, main commutator brushes on the line of magnetization of the inducing Winding connected in series with both stator windings, zation of the exciting winding, a transformer having its primary in series with the main brushes and its secondary in series with the exciting brushes, and means for impressing a shunt voltage on the main brushes, exciting winding, and transformer primary, in series, and for varying the amount of said voltage.

7. A single-phase motor of the commutator type having inducing and exciting windings on the stator connected in series with each Olillel,l1ltl"t coninmtatorbrushes on the line of na 'netization of the inducing winding having its primary in series with the main exciting brushes onthe line of inagnetibrushes and its secondary in series with the In Witness whereof, I have hereunto set exciting brushes, connections for placing the I my hand this 23rd day of December, 1907.

main brushes, exciting winding, and transformer primary, in a local closed circuit at starting, and means for introducing a shunt f voltage into said circuit when the motor has started. i

ERNST F. W. ALEXANDERSON. Vfitnesses:

BENJAMIN B. HULL, HELEN ()RFoRn. 

